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By D Craw

Interactions between structure and lithology in the Hyde-Macraes Shear Zone controlled the style of gold mineralisation at the Macraes mine. Large volumes of rock in some mine pits have most gold disseminated in hydrothermally altered schist, rather than in quartz veins. Mineralisation was initiated in the latter stages of metamorphism. Pods of massive schist rich in quartz and feldspar are surrounded by more fissile schist consisting of interlayered micaceous and quartzofeldspathic schist. Later shears have been partly controlled by the micaceous schist, and anastomose around pods of more massive schist. Micaceous schist was replaced by pyrite and arsenopyrite, accompanied by recrystallisation of phengitic muscovite under lower greenschist facies conditions. Gold occurs in sulfides and with microcrystalline quartz formed during minor silicification. Massive schist is locally mineralised along sulfidic microshears which have phengitic muscovite largely illitised under sub-greenschist facies conditions. Mineralised massive and micaceous schists were overprinted by cataclastic shears, with addition of graphite and more sulfides. Mineralisation occurred during a transition from ductile to brittle deformation regimes as the schist was uplifted in the late Jurassic.

Jan 1, 2004

Rock formation at shallow depths is generally associated with complex geology consisting of many joints, fractures, bedding planes, etc. Fragmentation results from primary blasts in such strata are therefore significantly influenced by structural discontinuities. To evaluate the role of discontinuities, which is of great use in the design of blasts in such conditions, a two-stage investigation program was taken up. In the first stage, model scale tests were conducted with single and double holes with the strike of discontinuities parallel and perpendicular to the face. Later, field studies were conducted in a limestone mine and a coal mine. Blast patterns were modified based on the results obtained from model scale blasts. Secondary blasting was taken as a measure to assess blast performance in the field, whereas mean fragment size, fine and coarse fragmentation indices were considered as fragmentation measures in model scale tests. Model tests indicated confinement of explosive energy by the discontinuities surrounding blasthole. Crater shape and size were significantly influenced by the orientation of joints with respect to the face. Modified blast designs with decreased burden x spacing patterns resulted in improved fragmentation in the field. A reduction of about 12 per cent in explosive consumption was recorded with modified blast designs. Boulder formation was observed to decrease by about 79 per cent as well.

Jan 1, 1995

By Saghafi A

Spoil piles are produced routinely in open cut coal mines. Spoil piles may contain waste coal and other carbonaceous horizons. Coal and carbonaceous materials react with oxygen in the atmosphere, producing heat. If the rate at which heat is generated is greater than the rate at which heat can be dissipated, the temperature of the spoil pile rises. If the heating remains unchecked, spontaneous combustion can occur. Spontaneous combustion poses significant safety, environmental and economic problems if it should become established in spoil piles. Using the basic features of self heating in spoil, the use of model is directed toward developing quantitative prediction of spontaneous combustion in open cut coal mine spoil Piles.

Jan 1, 1998

By Olson H, Kincaid R

The marine portion of the Pacific Basin and Rim constitutes a significant part of the world's surface in which the mineral resources are virtually undeveloped. Indications of substantial resources have resulted in speculation and uncertainty with regard to their potential in the near term. The main issues are centered on the markets for the resource materials, the technology needs for their recovery, and the possible impacts of their development on the environment. While the governments of Japan, France, the Soviet Union, India, China, and Korea are financing new programs in deep ocean mining, the US is consolidating its early leadership by the continuation of NOAA's authority under the Deep Seabed Hard Mineral Resources Act and the Sea Grant Act, Interior's authority under the outer Continental Shelf Lands Act, and by the development of a new Marine Minerals Technology Center within the Department of Interior's mineral institutes program, managed by the U.S. Bureau of Mines. The Center has a Continental Shelf Division (CSD) located in Mississippi, and an Oceans Basin Division (OBD) located in Hawaii. Research and training in the divisions is directed toward the practical aspects of mineral recovery from the nearshore and deep ocean environments with a strong bias for the OBD toward industrial and international cooperative programs in the Pacific Basin and Rim. In terms of resource development, the marine minerals in the Pacific Basin may be favored in some cases, in competition with land sources, by political and environmental considerations.

Jan 1, 1990

This paper carries on from an earlier paper 'Cemented fill practice and research at Mount Isa' and reports further on the laboratory programme at Mount Isa to develop a cheap cem- ented fill using Company waste products. The practical economic significance of availability of cheap cementing agents is re- viewed, with the various alternative approaches available The basic approach adopted within this paper is that use of reactive pozzolans such as ground slags to replace a proportion of the Portland cement in the fill can make mining methods employing cemented fill more economic- ally competitive with other mining methods.

Jan 1, 1973

By E Rubio, N Morales

Currently, mine plans are optimised by using several criteria as objective functions, like profit, life-of-mine, concentration of some pollutants, mining costs, confidence level or ore resources, with consideration of constraints related to production rates, plant capacities and grades. Whilst this approach is successful in terms of producing high value production schedules, it uses a static opening sequence of the drawpoints and therefore the optimisation is made within the level of freedom left by the original opening schedule, and as a result it is far from the true optimal value of the project. This paper presents a model to optimise the sequence of drawpoint opening over a given time horizon. The emphasis is in the precedence constraints that are required to produce meaningful operational sequences considering the exploitation method (panel or block caving), physics considerations and logical rules. Further on, while it applies the standard approach of maximising net present value (NPV), it considers other targets for optimisation, like the robustness and constructability of the plans. Finally, it applies the model to real data to obtain feasible plans by means of this model. The first tests were done varying the production capacity of the mine.

Sep 26, 2011

By E Y. Baafi

Artisanal and small-scale gold mining (ASSM) offers lucrative employment opportunities to the locals of most developing countries. The major drawback of ASSM is its adverse impacts on the environment resulting from improper mining and processing techniques. Papua New Guinea (PNG) has very active ASSM activities. The artisanal and small-scale gold mining in PNG provide employment at local and national levels and the sector is an important source for inflow of foreign exchange into rural communities. However, small-scale mining activities are associated with sensitive health and environmental issues. The process of recovering gold by retorting and heating the amalgam over an open fire is a dangerous health practice. This paper discusses artisanal and small-scale gold mining operations in PNG and their impacts on the local environment.

Jan 1, 2008

New Zealand is an exposed part of a sub- continent that was detached from Australia when the Tasman Sea opened in the Late Cretaceous. The pre-separation rocks occur in three main belts. A western belt or terrane was part of Antarctica, was continuous with southern Australian rocks, and was moved eastwards in the Mid Devonian. A central belt of Hokonui and Caples rocks can be correlated broadly with the Gympie Terrane of eastern Queensland. It was an island arc, fore-arc basin and accretionary wedge system, and it was accreted to eastern Australasia in the Mid Triassic. The third belt consists of Torlesse rocks and was possibly emplaced over the Caples rocks by at least three pulses of strike-slip, in the Triassic, the Jurassic and the Cretaceous. The three episodes of strike-slip can be correlated with regional events in eastern Australia. Pre-Cainozoic New Zealand was an amalgam of terranes that had moved eastwards from south of Australia and southwards from east of Australia.

Jan 1, 1987

TABLE OF CONTENTS:Introduction.Chemical Composition-lignitic coal-earthy coal-pollen coal-fern coal-nature of ash in the several coal types.Carbonization Tests.Air Drying of the Coal Types-rate of drying in the coal face-relative rates of diffusion-differential slacking of coal types-rate of oxygen absorption.Origin of the Coal Types-colour difference-cause of different rates of diffusion.Practical Significance.Summary.Acknowledgments.The Yallourn brown coal seam, where exposed in the Yallourn Open Cut, and the Latrobe brown coal seam, where exposed in the Yallourn North Open Cut, are both distinctly bedded. Close inspection shows that both seams consist of beds of coal from 1 to 10 ft. thick, which on drying out develop differences in colour and in their, shrinkage crack patterns. Tliese differences become apparent in the...

Jan 1, 1947

By Partridge A. C

Pinched Sluices, in a variety of guises, are used extensively for the separation of minerals according to density. In the authors' work a pilot-scale sluice has been constructed with provision for splitting the discharge stream into a number of layers. The composition and flowrate of the stream can thus be analysed as a function of depth and the results presented graphically. The effects of such parameters as total flowrate, pulp composition and particle size on overall performance can be clearly seen from such data.

Jan 1, 1979

A formalised approach to risk management has been regulated in the United Kingdom (UK) since the Construction (Design and Management) Regulations 1994 (CDM) came into force in 1995. These regulations have recently been revised in 2007. In response to a series of significant claims around the world the UK insurance industry published a code of practice for risk management of tunnels in 2003, and that was followed by an international version in 2006. Probably one of the main contributions of this new approach is the recognition that health and safety risks can best be addressed early in the process, initially by the owner and then by the designers. One of the aims is to achieve elimination of risks by good design. The advantage of a risk-based approach to tunnel design is that all risks are considered explicitly, and any residual risks in the design are communicated clearly to the construction team. This paper looks at the implementation of this formalised approach to risk management with reference to the A3 Hindhead Project. The design has been undertaken in accordance with the requirements of the CDM regulations, and also in compliance with the Joint Code of Practice for Risk Management of Tunnel Works in the UK. An outline of the risk-based design process used is provided, including examples.

Jan 1, 2008

By Enga B. E

Following considerable laboratory studies concerning diesel particulate control systems for underground use, a Canadian program was initiated to implement practical, real-life systems. This program covers the application in seven mines throughout Canada, of a particulate control system, to 14 engine models from four engine manufacturers in 18 different vehicle types, for a total of 23 vehicles. Partially funded by the Canadian National Research Council (NRC), this program required detailed analysis of operating cycles, maintenance variabilities and installation problems. This paper summarizes the work carried out to date to define real-world targets and the success achieved so far in attaining practical underground particulate control.

Jan 1, 1988

By R Lurf, C Weber

In the frame of this paper a holistic dynamic process model approach is presented in order to introduce operational and technical excellence in drilling and blasting. Both on a macro and micro level the single process parts of drilling and blasting are outlined and their interaction is explained. The use of this approach for closing the gap between process planning and process implementation is explained and an example of the value generated is given.

Jan 1, 2007

By T Berryman

The Fimiston reserve is being depleted at the rate of one million ounces per year; most of which is processed by the Fimiston plant, with the remainder being stockpiled. As for most other large open cut mines around the world, Fimiston has an excellent dispatch and tracking system. Reconciliation is used to determine how the various models used in mine planning (such as a reserve, budget and schedule models) are tracking against production. It is also used to gauge the performance of grade control estimation against production; however, analysing the results of this can be complicated and, at times, misleading. The reconciliation process involves adjusting the monthly production data to equal the mill reported tonnes and grade, plus the change in stockpiles. This adjusted number is then compared to the grade control reported tonnes and grade, the scheduled model (monthly planning model) tonnes and grade and against budget (Reserve) tonnes and grade. This paper includes explanations of all assumptions made in the reconciliation process, including the end of month closing stocks balance, the application of adjustment factors to the dispatch data to create a new balanced set of production data and the monthly sign off to comply with the Sarbanes-Oxley requirements of the North American owners. The reserve is reconciled by proved and probable classification. This tool is used to assess the robustness of the classification scheme utilised and identify any reconciliation issues as they arise. Within the Fimiston deposit there are still issues that are clouded by the assumptions made concerning the scale of observation, poor data support and the mining of the narrow lode areas of the deposit. The declared ore mined (DOM) number (which is defined in the paper) can be significantly affected by these assumptions, and these need to be clearly stated and understood when looking at the reconciliation data. The DOM tonnes and grade is a good indicator of real mine performance as it adjusts mined tonnes and grade to take into account the milled tonnes and grade each month, and prevents cumulative errors from building up in mine predicted dispatch numbers or end of period stockpiles. This number allows monthly monitoring of the mine to mill performance and allows valid comparisons to be made back to budgets and reserves over a period of time. KCGM uses three month rolling averages to monitor performance against reserve and budget models. This ensures that monthly distortions in the figures due to stockpiling issues or over mining in a particular period do not lead to false conclusions. Reconciliation performance over a longer period (12 - 18 months) is used to adjust reserve models should significant variance be observed. By closely monitoring the reconciliation performance at the Fimiston operation, fine tuning of all aspects of the grade estimation process from reserve through to grade control can be made. This allows the most accurate data to be used when planning from reserve data for the Life of Mine Plan through to grade control data for short-term mill feed.

Jan 1, 2006

By Resta S. A

Energy Resources of Australia Ltd - Ranger Mine is located about 255 kilometres east of Darwin in the Alligator Rivers Region of the Northern Territory. The Ranger project is surrounded by Kakadu National Park which is on the UNESCO World Heritage list. . Ranger Mine operates the largest uranium mine and processing plant in Australia. It is designed to produce 3000 tonnes of uranium oxide per year, but presently is producing a little less than one half that figure due to the depressed uranium market. The safety performance of the employees and Ranger as a whole continues to improve. The lost time injuries (LTI) have significantly reduced from 74 in 1985 to five in 1994. The total days lost due to LTIs have gone from 1543 to 14. These significant improvements have reflected directly on workers' compensation premiums in which a four-fold reduction has occurred. It is estimated that the actual monetary saving to the company is about $1.3 million per year and directly reports to the profit of the company. There is also an obvious and significant reduction in the less quantifiable costs such as the suffering of the injured employees and cost to society. The paper will review the various initiatives introduced and assess their effectiveness. Performance improvement is primarily dependent on the commitment, introduction of various initiatives and the subsequent change in workplace culture.

Jan 1, 1994

By Beattie MJV

Widely diverse mechanisms exist for the action of a range of selective sulphide flotation depressants. Collector desorp- tion, leaching, competitive adsorption, formation of hydrophilic reaction-product coatings, action as reducing agents, and action as lattice-oxidizing agents are discussed. Detailed attention is focused on the latter two mechanisms. Recent works on copper depressants particularly for copper-molybdenum separations, and oxidizing agents enabling arsenopyrite- pyrite separations, are presented and discussed.

Jan 1, 1984

In 1972, with the West Lyell Open Pit winding down, mining operations transferred underground. All development tunnelling until the end of the decade was carried out by a fleet of ten pneumatic Jumbos.A decision was made in 1980 to purchase an electric-hydraulic Jumbo and a second was purchased in 1982. Their introduction changed the face of development at Mount Lyell. Significant new demands were placed on main-tenance sections, particularly on electrical reticulation.Subsequently, two further electric-hydraulic Jumbos were purchased from Agnew Mining in 1984, and successfully overhauled and commissioned. As well, two electric-nydraulic production drilling rigs have been purchased. Only one of the original pneumatic Jumbos remains in service.

Jan 1, 1985

By Getliffe RK

It is becoming more and more difficult to operate mineral and metal processes profitably, as operating costs rise, quality demands in-crease, international competition becomes more fierce and Government charges remain at their current levels. Profitability today depends upon efficient operations, which can only be achieved through precise and dependable con-trol of each process unit comprising thetotal plant.Modern process control systems utilise distributed architecture with microprocessor-based controllers, data acquisition devices and VDU operator stations. Honeywell intro-duced this control technology in 1975 with the "Total Distributed Control" System. Now, building on the proven performance and re-liability inherent in TDC hiway modules, Honeywell has extended the TDC system to inte-grate both management information and control by providing distributed processing modules on the new TDC 3000 Local Control Network (LCN).

Jan 1, 1985

The laboratory-scale reduction of fixed beds of iron ore pellets has been investigated over a range of experimental conditions. The effects of reduction temperatures, gas compos- itions and flowrates on 1) the rate of reduction and 2) the physical properties of the metallized products after reduction are being studied as part of a general programme aimed at the evaluation of the use of gaseous reductants for the direct reduction of Australian iron ores. This paper deals primar- ily with the effects of temperature on the rate of reduction using a H2/CO gas mixture. The physical properties of the metallized products such as strength after reduction, abrasion resistance and porosity are presented as functions of the reducing temperature.

Jan 1, 1974

By M Ridd

The Pasminco Century Mine (PCML) is located 250 kilometres north-north-west of Mt Isa in Queensland. As one of the worldÆs largest zinc mines, PCML comprises mining and milling operations at Lawn Hill, concentrate filtering and shipping facilities at Karumba in the Gulf of Carpentaria, and a 304 km slurry pipeline connecting the two operations.Mineralisation at Century occurs in the upper part of the Lawn Hill formation and is comprised of siltstones, shale and sandstone. Pyrite occurs immediately above the mineralised sequence, and throughout the footwall carbonaceous shale forming the lower proportion of the deposit. Zinc predominantly occurs as sphalerite (ZnS) and lead as galena (PbS). These sulfides are very fine-grained and may oxidise rapidly upon exposure. The pyrite, sphalerite and galena are the main potential sources of acid rock drainage (ARD) or heavy metal leachate at the mine site.To minimise the generation of ARD in the waste rock dumps, they are constructed in a specific manner and waste rock is classified into the following three classes based on competence and acid forming/consuming capabilities:Class 1: Competent rock, non-acid forming or acid-consuming material. Class 2: Non-competent, non-acid forming or acid-consuming material. Class 3: Acid-forming material. The generalised Waste Rock Dump Design for current operations comprises an outer zone of Class 1 material and inner zone with Class 2 and 3 material. Limestone is the Class 1 material used for both its structural support and acid neutralising capacity. Reserves of limestone at the mine site are limited. Net acid generation (NAG) tests confirm that a mix of limestone and shales can be net acid consuming.Field based and laboratory based trials have been established at PCML to quantify blending levels of limestone and shale that will produce leachates both neutral in pH and low in metal/salt concentrations. This paper will discuss the first six months results (of a two-year sampling program) from the trials.

Jan 1, 2004